1. Field of the Invention
This invention relates to a pneumatic tire, and more particularly to a high-running performance tire having an effectively improved resistance to hydroplaining on wet road surface while maintaining a steering stability on dry road surface at a sufficiently high level.
2. Description of Related Art
As this type of the tire, there is widely known a combination of a plurality of straight circumferential grooves extending in a circumferential direction of a tread and a plurality of slant grooves extending slantwise and upward from the vicinity of a center of the tread toward a tread end in a tread pattern viewed from a front of the tire mounted onto a vehicle.
In such a conventional tire, when a negative ratio of the groove is increased or an angle of each slant groove inclined with respect to the circumferential direction of the tread is made small in order to improve the resistance to hydroplaining on wet road surface, problems result in that the effective ground contact area of land portions in the tread is decreased and the rigidity of a block against force in widthwise direction of the tread is reduced to lower the steering stability on dry road surface.